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>27.3. Viewing Locks</A
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>   Another useful tool for monitoring database activity is the
   <TT
CLASS="STRUCTNAME"
>pg_locks</TT
> system table.  It allows the
   database administrator to view information about the outstanding
   locks in the lock manager. For example, this capability can be used
   to:

   <P
></P
></P><UL
><LI
><P
>      View all the locks currently outstanding, all the locks on
      relations in a particular database, all the locks on a
      particular relation, or all the locks held by a particular
      <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> session.
     </P
></LI
><LI
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>      Determine the relation in the current database with the most
      ungranted locks (which might be a source of contention among
      database clients).
     </P
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><LI
><P
>      Determine the effect of lock contention on overall database
      performance, as well as the extent to which contention varies
      with overall database traffic.
     </P
></LI
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><P>

   Details of the <TT
CLASS="STRUCTNAME"
>pg_locks</TT
> view appear in
   <A
HREF="view-pg-locks.html"
>Section 45.56</A
>.
   For more information on locking and managing concurrency with
   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>, refer to <A
HREF="mvcc.html"
>Chapter 13</A
>.
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